Wallflower Patrick Saint has always taken second place to his cocky, bullying, football-star of a best friend, Kelly McDermott, who seems to have everything. Patrick, meanwhile, feels stuck in a time warp, forced to live in the shadow of his brother, who died years before. When Kelly wakes up one morning stark naked and behaving completely at odds with his old self, Patrick knows something’s up: Kelly’s now thoughtful, seemingly caring and intelligent. What gives? Kelly explains that he’s returned from 20 years in the future to right a wrong he committed as a teen and possibly save the world. Dorfman spins brilliant sentences, packing big ideas, philosophy, the sounds of jazz and pure energy into the dialogues between the two boys. His plot may require some serious suspension of disbelief, but it moves at full throttle despite some jerks and stops in the time-travel elements. The voices are mostly even, though at times the characters feel too world-wise for their age. A wild, thought-provoking, heartbreaking jolt of a ride through astrophysics, friendship, Armani suits and heartache. (Science fiction. YA)